This invention is an improvement on combination weighing machines of the type that are disclosed in U.S. Pat. Nos. 4,630,695, 4,901,807, 5,258,580 and 5,258,581. These prior art machines, used mainly in the food industry, are controlled by microprocessors and function at tremendous speeds. In these prior art combination weighing machines, a target package weight is preselected. Fractional amounts of the target package weight, referred to as product batches, are metered through a plurality of product batch handling units. Each separate product batch handling unit includes a set of product batch handling devices, such as a feeder tray, an accumulation chamber and a weighing mechanism. As disclosed in the above prior art U.S. Patents, product batch handling units can include additional product batch handling devices, for example holding chambers. Each weighing mechanism weighs the product batch that has been metered to it and stores the identity and weight of the individual batch. The microprocessor then calculates how the weighed batches can be combined to best meet the target package weight. After the best combination has been selected, the product batches of the selected product batch handling units are discharged into a collecting hopper. The product batch handling units that were discharged are then filled with new product and the process is repeated. This is a well known process and reference may be made to the above identified patents for a more detailed disclosure of such apparatus. U.S Pat. Nos. 4,63,695, 4,901,807, 5,258,580 and 5,258,581 are hereby incorporated by reference as a part of this disclosure.
As is best illustrated in FIG. 5 of U.S. Patent No. 5,258,281, the mechanisms for imparting movement to the distributor, vibration to the feeder tray and the weigh cells for the weighing mechanism are all carried by a horizontal plate which is part of the machine flame. This horizontal plate and the operating mechanisms carried thereby are open to the environment surrounding the weighing machine. Although the trays, chambers and buckets are mounted through quick attach connections which allow them to be disconnected and thoroughly cleaned it is difficult to maintain the support area for the operating mechanisms clean.
Although food articles being processed by combination weighing machines does not have direct contact with the operating mechanisms or their support areas, it is important to provide a clean environment for the entire food processing area. For this reason, it is important that the operating components area be protected to avoid contamination to the food being processed.
To achieve these and other objectives, the present invention provides for a new and unique combination weighing machine chassis that is comprised of an enclosed hollow support member having an inner surface upon which the operating components are carried. There are openings formed in the hollow support member, including seals, through which the necessary drives and controls extend. Thus, air and water carried contaminates do not reach the operating components. As a result of this construction, when the trays, chambers and buckets are removed for cleaning, the outer surface of the hollow support member can be easily cleaned. The continuous flat outer surface of the hollow support member is accessible and does not have cracks and crevasses that are difficult to clean.
Another advantage of this unique combination weighing machine chassis is that the operating components are now housed in a closed compartment where they are protected from contamination by air and water borne debris such as oil and food.
Still another advantage of this unique combination weighing machine chassis is that the vibrator mechanism for the feeder tray is resiliently suspended from the top portion of the hollow support member which provides an improved vibrator mounting arrangement.